Validates cast before applying transformation (#12)

* bumps version

* Adds input cast validation to `transformer`

Whenever a cast is consumed from `transformer`, a cast validation is now
performed.

This commit makes even more natural to develop the commands as the developer
doesn't need to worry about receiving invalid casts.

Naturally, that's the expectation - there might exist a case when a
a command could potentially *want* to receive an invalid cast (which is
not the situation right now).

Author: Ciro S. Costa

VERSION

@@ -1 +1 @@
-0.0.5
+0.0.6

commands/transformer/transformer.go

@@ -106,6 +106,13 @@ func (m *Transformer) Transform() (err error) {
 		return
 	}
 
+	_, err = cast.Validate(decodedCast)
+	if err != nil {
+		err = errors.Wrapf(err,
+			"invalid input cast")
+		return
+	}
+
 	err = m.transformation.Transform(decodedCast)
 	if err != nil {
 		err = errors.Wrapf(err,

commands/transformer/transformer_test.go

@@ -111,4 +111,85 @@ var _ = Describe("Transformer", func() {
 			})
 		})
 	})
+
+	Describe("transform", func() {
+		var (
+			trans  *transformer.Transformer
+			input  string
+			output = "/dev/null"
+			err    error
+		)
+
+		JustBeforeEach(func() {
+			trans, err = transformer.New(
+				&DummyTransformation{},
+				input,
+				output)
+			Expect(err).To(Succeed())
+		})
+
+		AfterEach(func() {
+			os.Remove(input)
+		})
+
+		Context("with malformed input", func() {
+			BeforeEach(func() {
+				input, err = createTempFileWithContent("malformed")
+				Expect(err).To(Succeed())
+			})
+
+			It("fails", func() {
+				err = trans.Transform()
+				Expect(err).ToNot(Succeed())
+			})
+		})
+
+		Context("with malformed event stream", func() {
+			BeforeEach(func() {
+				input, err = createTempFileWithContent(`{"version": 2, "width": 123, "height": 123}
+[1, "o", "aaa"]
+[3, "o", "ccc"]
+[2, "o", "bbb"]`)
+				Expect(err).To(Succeed())
+			})
+
+			It("fails", func() {
+				err = trans.Transform()
+				Expect(err).ToNot(Succeed())
+			})
+		})
+
+		Context("with well formed event stream", func() {
+			BeforeEach(func() {
+				input, err = createTempFileWithContent(`{"version": 2, "width": 123, "height": 123}
+[1, "o", "aaa"]
+[2, "o", "bbb"]
+[3, "o", "ccc"]`)
+				Expect(err).To(Succeed())
+			})
+
+			It("succeeds", func() {
+				err = trans.Transform()
+				Expect(err).To(Succeed())
+			})
+		})
+	})
 })
+
+func createTempFileWithContent(content string) (res string, err error) {
+	var file *os.File
+
+	file, err = ioutil.TempFile("", "")
+	if err != nil {
+		return
+	}
+	defer file.Close()
+
+	_, err = file.Write([]byte(content))
+	if err != nil {
+		return
+	}
+
+	res = file.Name()
+	return
+}